In this work we studied the modification of the droplet size and distribution of stable parenteral emulsions (PEs) by microfiltration. The intravenous nutrition through PE needs to be conducted using very fine emulsified fat droplets, which have to be for health reasons at a mean diameter under 1 mum. In this work we used membrane microfiltration to decrease the fat particles mean diameter and distribution. The PE filtration was possible without coalescence, because of the high stability of the PE prepared by using an emulsification method never applied before to this type of emulsion. The membrane filtration process was carried out by using ceramic membranes with different pore sizes (0.8, 1.2 and 1.4 mum of mean pore radius). The results obtained showed that the shearing forces and trans-membrane pressure had a fundamental influence on the emulsion droplet size distribution and that depending on the membrane type or operating conditions used, the mean droplet size and distribution could be effectively decreased. (C) 2003 Elsevier B.V. All rights reserved.